The present invention relates to a capacitance sensing device suitable for use in applications where the presence of a substance to be measured, such as, the engine oil or the level of refrigerant in the refrigerating cycle in an automobile is detected by means of capacitance changes.
As an example of this type of devices for detecting capacitance changes, a device is known in the art in which opposed electrode plates are inserted into a liquid or a substance to be measured and the electrode plates are connected to an electric circuit section by lead wires, thus detecting changes in capacitance existing between the electrode plates. However, in the case of this device, the distributed capacitance and the stray capacitance are subject to variation depending on the length, shape, etc., of the lead wires leading from the electrode plates to the electric circuit section and consequently it is difficult to accurately detect any change in the capacitance existing between the electrode plates if the change is very small. Moreover, in the case of mass production, the capacitance of each of the devices must be adjusted properly.